Residues of environmentally derived toxaphene were determined in fish samples from the Great Lakes and from rivers of the southeastern United States. These analyses were performed by fused silica capillary gas chromatography with electron capture detection. Data reduction and compilation were performed using an “in-house” developed data base system. In an effort to more clearly delineate the similarity of environmentally derived toxaphene residues to technical toxaphene, SIMCA, a principal components pattern recognition technique, was used to analyze sample residues. The results of these analyses are discussed.